Apparatus for protecting the field structure and windings of dynamoelectric machines



APPARATUS FOR PROTEC W. F. DAWSON. TING THE FIELD STRUCTURE AND wmomes0F ELECTRIC MACHINES. APPLICATION FILED IUNE x6, 19l9.

DYNAMO Patented June 7, 1921.

Adjustabl e Inventor: William F. Dawson,

His fitter-e3.

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V Be itknownthatfi; wnnm Fxm'ws'on, a citizen of thj Unit Statestesiaing at L rm, in tee-tenet" 'of "-*Essek,Statefoftssachusettsghavejinvtnted mtainnew' v 'nseful -lmprgofvenient s inApparatus for Protecting the it1d "Str1ietute-am Wi, nd

ings of Dyfhamo iEiectr-ic Machines;- the follewin is a spe'cificatiorizx 'Myfintenhon relatesf 'to apparatus for protection 62f he heldstrucmreand'wind; ingsoi "a *dy'nainoelectric niachine'rsupp'lying adistribution circuit" from the "in'urious My "liveiftion is especially?hpp'licable to the-protection 0 the fielfd 'structure and windings of apdly hesealternating current 2 0 generatprfro n the injurious effects ofoperat v. i "th r rt h b I 1y u b lanl'd'as may ea a sieglepliaeetit-seem stppnee i ewe e, unba a ed; e1 ge 0 E1 @fl i t qtm i mi t cthe; old winding andthe nure the phasesf are unhalancedttlie' 151 7851is this induced Q Q -i This iifldil'ced v l gev 11 3 he 5 sol a'r e asto 'break.down the iii'sulation of the l fie d'windi rig. 'and "reduce ashort cirmanates serious wa e to gth e "field windinh *urthe'rmore; theeddy" currents in the eld structure caused by this induced voltagemay'prod ceexces'siveand disastrous T D i P O myin n hu is to prev n thefield structure-"and windings of the'dyna moflei'fctri ,in achine beingdauiaged by the presence tisuthtbnomt 1condit1ons on the distributioncircuit In accordance with this object I provide means 7 K 4, responsiveto the current produced by the voltage induced in theffield circuit bythe abnormal conditions for rendering the dynamo electric ma-' to thechine imperative to supplycurrent distribution circuit..

The single figure of the accompany ng drawing is a diagrammatic view, ofa polyphase System V of distribution showing one embodiment o f myinvention.

Referring to the drawing, polyphas'e cur- Specification of; Letterslctentmana ements, Assmnon TO Gunman murmur; aconaona'rronw NEW YORK. It 5 =1 i v vi; EQDF WWWWAND IHGS 0E mmmm- W P31QN 93WE 1 1;;

iPatented' J une" '7', 192i. 5 5 '1ere.-s""1 it edema refitis supiiliedfroni the p 01 n: crater -1 Vtoi'the olyphase distzihution in :cui t2-throught e oil switchg3. This oilswltch inay be oflany'well-knowntypegl The articular type shownin the drawing eonsists ofstat-iqn rycontact members i and 5, *mo'xjable contact inembers 6 carried by a bar7 and-arrangedto connectthe contact members 4min Eito coin letethecircuit between the, generator lf'a'n the distribution circuit 2, thelatch 8 "arranged to hold the oil switch closed, "a .tr'ippi n' coil 9for releasing the 'lat'ch'8, asprmg 10 arranged to be under tension'when the'oil switch is closed so as to open th oil'switch when the latchis released and means (not shown) for closing the bi switch." Theclosingmeans usually consists eta magnet arranged when energizedto rnovethe bar7"so as to bring the movable "contact members 6 into eng a ement n'th'theicontact members 4 and 5. o closng means is' s'hown in the"drawing because "it does no't'con'stitute apart of this inventionThegeneratdr 1 is provided with a field winding 14 connected to thedirect current exeite'rugyhiehis plrovided'hvith a shunt fieldvv1nd1iigf 16. "I ave shown an adjustable resistance 1'? connected inseries with the generator field circuit so that the exciting current canbe readily adjusted'to any desiredvalueL V In th'e'fild circuit fof thegenerator, I provide'suitable means; which is responsive to pulsatingcurrent, but is not afiected byjdirect c'urrent, for rendering thedynamo electric machine 1 inoperative to supply current to thedistribution circuit 2 in case the voltage induced inth field winding ofthe dynamo electric machine by abnormal conditions he distributioncircuit exceeds a predetermined value. In the specific embodiment of myinvention shown in the drawing, this means comprises an inductive devicesuch as a reactor 18 connected in 95 series with the field winding ofthe enerator and a tripping coil 9 for the oi circuit breaker 3connected in shunt with the re construction sh wn 1n the drawing, shapedcore w1 an E th the winding, w 1c consists of a few turns, on the middleleg of the core and an armature adjustable relative to the core so thatthe reluctance of the mag. netic circuit can be readily adjusted to anydesired value.

The resistance of the tripping coil is much larger than the resistanceof the reactor 18, whereas the reactance of the tripping coil is verysmall. In order to adjust the resistance of the tripping coil 9 I preferto insert a variable series resistance 20 in the circuit 'thereof. Theresistance of the reactor is made small so that the voltage across theterminals is low under normal conditions as only direct current flowsthrough the field circuit. If, however, there is a bad unbalanciii ofthe hases, the field winding 14 will ave a vo ta e of double the normalfrequency induce therein. This induced voltage causes an alternatingcurrent of the same frequency to flow through the field circuit, therebyincreasing the reactance of the reactor 18. Consequently the voltage droacross the reactor increases so that the v0 tage across the terminals ofthe tripping coil 9 is also increased, causing more current to flowthrough the tripping coil 9. By properl adjusting the air gap of thereactor 18 an the resistance 20 the tripping coil 9 can be made to tripopen the oil switch 3 when the magnitude of the voltage induced in thefield approaches a dangerous value thereby rendering the dynamo electricmachine 1 inoperative to supply. current to the distribution circuit 2.In this way I am able to prevent theinduced voltage from damaging thefield winding, and the field structure being damaged by the eddycurrents set up by the double frequency voltage. I also prefer to inserta rela 21 in series with the tripping coil 9. Tliis relay is desi ned torespond .toa smaller current than t e tripping coil 9, and when operatedcloses a circuit for the signal 22. In this Way a signal is operatedbefore the oil switch is opened, and therefore will give the operator achance to clear the circuits from unbalanced operation beforethe oilswitch trips out.

While I have illustrated and described a reactor in the fieldcircuit itwill be obvious to those skilled in the art that my invention is notlimited to such voltage producing means but contemplates the provisionof any device or combination of devices and circuits for performing asimilar function in the combination.

It will also be obvious to those skilled in the art that my invention isnot limited to the particular arrangement shown for rendering theenerator inoperative to supply current to t e distribution circuit, butcontemplates the utilization of any means which will perform thisfunction in the com ination. I intend therefore to cover all suchmodifications the spirit of m and Variations as fall within inventionthe scope of which is defined in t e appended claims.

at I claim as new and desire tosecure by Letters Patent of the UnitedStates, is

1. In combination, a distribution circuit, a dynamo electric machinesupplying electrical energy thereto, and means responsive to the currentproduced by the voltages induced in the field windings of said machineby abnormal conditions in said distribution circuit for disconnectingsaid machine from said distribution circuit.

In combination, a polyphase distribution circuit, a polyphase generatorsupplying electrical energy thereto, and means responsive to the currentroduced by the voltage induced in the fied windin s of said machine by apredetermined unba ancing of the phases for disconnecting said generatorfrom said distribution circuit.

3. In combination, a distribution circuit,

a dynamo electric machine supplying electrical ener y thereto, and aninterru tor for disconnecting said machine from sai distribution circuitcomprising relatively movable contact members, a reactor in the fieldcircuit of said machine, and a trip coil connected in shunt relation tosaid reactor and arranged to separate said contact members i when thecurrent produced by the voltage induced in said field circuit byabnormal conditions in said distribution circuit exceeds a predeterminedamount.

4. In combination, a tion circuit, a polyphase generator supplyingelectrical energy thereto, and an interrupter for disconnecting saidmachine from said distribution circuit comprising relatively movablecontact members, a reactor in the field circuit of said generator, and atrip coil connected in shunt relation to said reactor and' arran ed tobe operated by. the current produced by the voltage induced in saidfield circuit by a predetermined unbalancing of the phases to separatesaid contact members.

5. In combination, a polyphase distribution circuit, a polyphasegenerator supplyin electrical energy thereto, a reactor connecte in thefield circuit of said generator, and an electromagnetic device connectedin shunt relation to said reactor and arranged to be operated by thecurrent produced by the voltage induced in saidfield circuit by apredetermined unbalancing of the phases.

6. In combination, a polyphase distribution circuit, a poly hasegenerator supplying electrical energy t ereto, and means responsive tothe electromotive force induced in the field circuit of said generatorby the unbalancing of the phases of said distribution circuit forrendering the generator inoperative to supply current to saiddistribution circuit.

polyphase distribuv 7. In combination, a polyphase distribuin said fieldcircuit by a redetermined untion circuit, a polyphase generwtorsupplying balancing of the phases 0 said distribution electrical energythereto, StIl-iIldUOtlVe device circuit.

connected in the field circuit of said genera- In witness whereof I havehereunto set my 5 tor, and an electromagnetic device connected hand thls13th day of June, 1919.

to said inductive device and arranged to be operated in response to thevoltage induced WILLIAM F. DAWSON.

